A little off topic, but I'm working on doing something similar to my QT:
I run auto water changes daily - about 1/2 a gallon give or take. I will soon be plumbing the "waste" water (almost ULNS) to run into the QT instead of down the drain. The QT will then overflow into the drain. This way there's no risk of QT to tank infection, there's some but minimal nutrients going in and the QT should keep similar parameters to the Display system. There may be the need for the odd manual water change, probably before adding new fish, but during the quarantine process, it will be acclimating to tank parameters.
As for invert QT, I've never bothered. Probably never will. After the QT is working, I'm revamping my Culture/Breeding station so maybe ill be looking for a project like a coral QT & frag tank.